Refrigeration cycle device

ABSTRACT

According to one embodiment, a refrigeration cycle device includes a refrigeration cycle with a plurality of expansion valves and a detector. The detector predicts a first total degree of opening of the valves at a first time point on the assumption that there is no refrigerant leakage in the cycle, based on a change to a first state quantity of the cycle at the first time point from a second state quantity of the cycle at a second time point. The detector detects refrigerant leakage of the cycle by comparing the first total degree of opening with a second total degree of opening which is an actual total degree of opening of the valves at the first time point.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation application of PCT Application No.PCT/JP2015/050355, filed Jan. 8, 2015 and based upon and claiming thebenefit of priority from Japanese Patent Application No. 2014-028425,filed Feb. 18, 2014, the entire contents of all of which areincorporated herein by reference.

FIELD

Embodiments described herein relate generally to a refrigeration cycledevice which deals with the leakage of a refrigerant.

BACKGROUND

In a refrigeration cycle which returns a refrigerant discharged from acompressor to the compressor via a condenser, a pressure reducer and anevaporator, the refrigerant may leak from, for example, a connectionportion of pipes through which the refrigerant passes. The refrigerationcycle is required to detect such leakage of refrigerant accurately.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing the structure of a refrigeration cycledevice according to a first embodiment.

FIG. 2 is a p-h chart showing the behavior of a refrigeration cycle inthe first embodiment.

FIG. 3 shows the relationship between the progression of refrigerantleakage and the degree of opening of expansion valves in therefrigeration cycle.

FIG. 4 is shown for explaining an example of a method of detectingleakage in the first embodiment.

FIG. 5 is a flowchart showing an example of an operation which isperformed when cooling is applied in the first embodiment.

FIG. 6 is a flowchart showing an example of an the first embodiment.

FIG. 6 is a flowchart showing an example of an operation which isperformed when heating is applied in the first embodiment.

FIG. 7 is a conceptual diagram showing an example of the relationshipbetween the operating rate and the possibility of implementation ofleakage determination in the above heating operation.

FIG. 8 is a flowchart showing an example of an operation of updating asetting value used for comparison with the operating rate.

FIG. 9 is shown for explaining an example of a method of detectingleakage in a second embodiment.

FIG. 10 shows the results of the calculation and measurement of thetotal amount of supercooling in the second embodiment.

FIG. 11 is a flowchart showing a modification example of an operationwhich is performed when cooling is applied.

FIG. 12 is a flowchart showing a modification example of an operationwhich is performed when heating is applied.

DETAILED DESCRIPTION

In general, according to one embodiment, a refrigeration cycle devicecomprises a refrigeration cycle which returns a refrigerant dischargedfrom a compressor to the compressor via a condenser, a plurality ofexpansion valves and a plurality of evaporators connected to theexpansion valves, respectively. The refrigeration cycle device furthercomprises a detector which predicts a first total degree of opening ofthe expansion valves at a first time point on the assumption that thereis no refrigerant leakage in the refrigeration cycle, based on a changeto a first state quantity of the refrigeration cycle at the first timepoint from a second state quantity of the refrigeration cycle at asecond time point earlier than the first time point. The detectordetects refrigerant leakage of the refrigeration cycle by comparing thefirst total degree of opening with a second total degree of openingwhich is an actual total degree of opening of the expansion valves atthe first time point.

Some embodiments will be described hereinafter with reference to theaccompanying drawings. Each embodiment exemplarily shows a refrigerationcycle device mounted in an air conditioner.

[1] First Embodiment

A first embodiment is explained.

As shown in FIG. 1, an air conditioner comprises a plurality of outdoorunits A1, A2, . . . , An, and a plurality of indoor units B1, B2, . . ., Bm. Thus, outdoor units A1 to An and indoor units B1 to Bm areprovided in the multi-type air conditioner.

Each of outdoor units A1 to An comprises a compressor 1, a four-wayvalve 2, an outdoor heat exchanger 3, an outdoor expansion valve 4, aliquid receiver 5, packed valves 7 and 8, an accumulator 9, an inverter10, an outdoor fan 11, pressure sensors 12 and 13, and temperaturesensors 14, 15, 16 and 17. Each of indoor units B1 to Bm comprises anindoor expansion valve 31, an indoor heat exchanger 32, an indoor fan 33and a temperature sensor 34.

In each of outdoor units A1 to An, the outdoor heat exchanger 3 isconnected to the discharge hole of the compressor 1 via the four-wayvalve 2, using pipes. Packed valve 7 is connected to the outdoor heatexchanger 3 via the outdoor expansion valve 4 and the liquid receiver(in other words, the liquid tank) 5, using pipes.

The indoor expansion valves 31 of indoor units B1 to Bm are connected topacked valves 7 of outdoor units A1 to An, using pipes. In each ofindoor units B1 to Bm, the indoor heat exchanger 32 is connected to theindoor expansion valve 31, using pipes. Packed valves 8 of outdoor unitsA1 to An are connected to the outdoor heat exchangers 32 of indoor unitsB1 to Bm, using pipes. In each of outdoor units A1 to An, the suctionhole of the compressor 1 is connected to packed valve 8 via the four-wayvalve 2 and the accumulator 9, using pipes. A heat pump refrigerationcycle is formed by these connections. Outdoor units A1 to An and indoorunits B1 to Bm are connected in parallel with each other.

The compressor 1 is a closed compressor in which a motor operated by theoutput of the inverter 10 is housed in a closed case. The compressor 1sucks a refrigerant which passed through the accumulator 9. Thecompressor 1 compresses the sucked refrigerant and discharges it fromthe discharge hole. The inverter 10 converts the voltage of commercialAC power supply into DC voltage. The inverter 10 converts the DC voltageinto AC voltage having a predetermined frequency F (Hz) and a levelbased on the predetermined frequency F, and outputs the AC voltage.

In a cooling operation, as shown by the arrows, a refrigerant dischargedfrom the compressors 1 of outdoor units A1 to An flows into the indoorheat exchangers 32 of indoor units B1 to Bm via the four-way valves 2,the outdoor heat exchangers 3, the outdoor expansion valves 4, theliquid receivers 5 and packed valves 7 of outdoor units A1 to An and theindoor expansion valves 31. The refrigerant flowing from the indoor heatexchangers 32 is sucked by the compressors 1 after passing throughpacked valves 8, the four-way valves 2 and the accumulators 9 of outdoorunits A1 to An. By this flow of refrigerant, each outdoor heat exchanger3 functions as a condenser, and each indoor heat exchanger 32 functionsas an evaporator.

In a heating operation, the refrigerant discharged from the compressors1 of outdoor units A1 to An flows into the indoor heat exchangers 32 ofindoor units B1 to Bm via the four-way valves 2 and packed valves 8 ofoutdoor units A1 to An by switching the flow channels of the four-wayvalves 2. The refrigerant flowing from the indoor heat exchangers 32 issucked by the compressors 1 after passing through the indoor expansionvalves 31 of indoor units B1 to Bm, and packed valves 7, the liquidreceivers 5, the outdoor expansion valves 4, the outdoor heat exchangers3, the four-way valves 2 and the accumulators 9 of outdoor units A1 toAn. By this flow of refrigerant, each indoor heat exchanger 32 functionsas a condenser, and each outdoor heat exchanger 3 functions as anevaporator.

In each of outdoor units A1 to An, the outdoor fan 11 is provided nearthe outdoor heat exchanger 3. In each of indoor units B1 to Bm, theindoor fan 33 is provided near the indoor heat exchanger 32.

In each of outdoor units A1 to An, pressure sensor 12 is attached to ahigh-pressure-side pipe between the discharge hole of the compressor 1and the four-way valve 2. Further, pressure sensor 13 is attached to alow-pressure-side pipe between the accumulator 9 and the suction hole ofthe compressor 1. Pressure sensor 12 detects pressure Pd of the abovehigh-pressure-side pipe. Pressure sensor 13 detects pressure Ps of theabove low-pressure-side pipe.

In each of outdoor units A1 to An, temperature sensor 14 is attached tothe high-pressure-side pipe. Temperature sensor 15 is attached to thelow-pressure-side pipe. Further, temperature sensor 16 is attached apipe provided between the outdoor heat exchanger 3 and the outdoorexpansion valve 4 at a position closer to the outdoor heat exchanger 3.Temperature sensor 14 detects temperature Td of the refrigerantdischarged from the compressor 1. Temperature sensor 15 detectstemperature Ts of the refrigerant to be sucked by the compressor 1.Temperature sensor 16 detects temperature T1 of the refrigerant flowingthrough the pipe between the outdoor heat exchanger 3 and the outdoorexpansion valve 4. Temperature sensor 17 is attached to, for example, aposition such that it is not in contact with the outdoor heat exchanger3 and receives air sent from the outdoor fan 11. Temperature sensor 17detects the outside air temperature To.

In each of indoor units B1 to Bm, temperature sensor 34 is attached to apipe provided between the indoor expansion valve 31 and the indoor heatexchanger 32. Temperature sensor 34 detects temperature T2 of therefrigerant flowing through the pipe between the indoor expansion valve31 and the indoor heat exchanger 32.

The outdoor expansion valves 4 and the indoor expansion valves 31 are,for example, pulse motor valves (PMV) in which the degree of openingchanges in accordance with the number of input drive pulses.

A controller 40 is connected to outdoor units A1 to An and indoor unitsB1 to Bm. A remote-control operation device (in other words, a remotecontroller) 41 and a reset switch 42 are connected to the controller 40.The controller 40 comprises, for example, a processor, a memory, acontrol circuit board and various circuits. For example, the remotecontroller 41 is used to set the operation conditions of the airconditioner. The reset switch 42 is provided in the control circuitboard provided in the controller 40, etc.

The controller 40 mainly functions as the following portions (1) to (3).These functions are realized when the processor included in thecontroller 40 executes the computer program stored in the memory.

(1) The controller 40 functions as a detector which calculates(predicts) a predictive total degree of opening (a first total degree ofopening) Qpre of the expansion valves at the present time point (a firsttime point) on the assumption that there is no refrigerant leakage inthe refrigeration cycle, based on the change to the state quantity (afirst state quantity) of the refrigeration cycle at the present timepoint from the state quantity (a second state quantity) of therefrigeration cycle in the early phase of operation (a second timepoint) earlier than the present time point. The detector detectsrefrigerant leakage of the refrigeration cycle by comparing thepredictive total degree of opening Qpre with the actual total degree ofopening (a second total degree of opening) Qact of the expansion valvesat the present time point. When heating is applied, the detector detectsrefrigerant leakage on condition that the operating rate R of indoorunits B1 to Bm is higher than a setting value Rs related to theoperating rate.

(2) The controller 40 functions as a recorder which records, in theearly phase of operation of the refrigeration cycle, the state quantityused by the detector to calculate the predictive total degree of openingQpre.

(3) The controller 40 functions as an updater which updates settingvalue Rs in accordance with the operating rate of indoor units B1 to Bmwhen heating is applied.

When cooling is applied, the total degree of opening Qact is the totaldegree of opening of the indoor expansion valves 31. When heating isapplied, the total degree of opening Qact is the total degree of openingof the outdoor expansion valves 4. Thus, when either cooling or heatingis applied, the total degree of opening Qact is the total degree ofopening of the expansion valves provided immediately before theevaporators (specifically, the indoor heat exchangers 32 in a coolingoperation, and the outdoor heat exchangers 3 in a heating operation) inthe direction of the refrigerant flow. The opening degree of eachexpansion valve is shown by, for example, the number of drive pulses ofthe expansion valve. In this case, the total degree of opening Qact isthe sum of the numbers of drive pulses of the expansion valves providedimmediately before the evaporators. The predictive total degree ofopening Qpre is also shown by the number of drive pulses.

A method of calculating the predictive total degree of opening Qpre isexplained.

In general, the degree of opening (the coefficient of discharge) Q of anexpansion valve provided immediately before an evaporator can beobtained by the following theoretical formula of the flowcharacteristic. Here, ρ is the density (kg/m³) of the refrigerant on therefrigerant inlet side of the expansion valve. L is the circulatingvolume (kg/s) of the refrigerant passing through the expansion valve. ΔPis the difference (MPa) between the pressure of the refrigerant on therefrigerant inlet side of the explain valve and the pressure of therefrigerant on the refrigerant outlet side.

Q=L×(1/ρ×ΔP)̂0.5

The circulating volume L and the pressure difference ΔP except thedensity ρ of the refrigerant can be calculated by using the operatingfrequency of the compressor 1, the temperature of the refrigerant on theoutlet side of the expansion valve provided immediately before theevaporator, the condensation temperature, the evaporation temperatureand the degree of superheating. Assuming that there is no refrigerantleakage, and the density ρ of the refrigerant is constant, the degree ofopening Q at the present time point can be predicted by correcting thedegree of opening Q at some time point based on the change from theoperating frequency, the temperature of the refrigerant on the outletside of the expansion valve provided immediately before the evaporator,the condensation temperature, the evaporation temperature and the degreeof superheating at that point to these parameters at the present timepoint.

Specifically, the predictive total degree of opening Qpre (the totaldegree of opening of the indoor expansion valves 31) is given by

Qpre=a1·ΔFsum+b1·ΔTcj ave+c1·ΔTg ave+d1·ΔTu ave+e1·ΔSHave+Qsum,  (1)

where a1, b1, c1, d1 and e1 are constants and may be determinedexperimentally, theoretically or empirically.

ΔFsum is the change in the sum Fsum of the operating frequencies F ofthe compressors 1.

ΔTcj ave is the change in mean value Tcj ave of the refrigeranttemperature Tcj on the outlet side of the expansion valves providedimmediately before the evaporators. When cooling is applied, therefrigerant temperature Tcj used to calculate mean value Tcj ave istemperature T2 detected by temperature sensors 34 of operating indoorunits B. When heating is applied, the refrigerant temperature Tcj usedto calculate mean value Tcj ave is temperature T1 detected bytemperature sensors 16 of operating outdoor units A.

ΔTg ave is the change in mean value Tg ave of the condensationtemperature Tg converted from the discharge pressure of the compressors1. Specifically, the condensation temperature Tg used to calculate meanvalue Tg ave is the temperature converted from detection pressure Pd ofpressure sensors 12 of operating outdoor units A.

ΔTu ave is the change in mean value Tu ave of the evaporationtemperature Tu converted from the suction pressure of the compressors 1.Specifically, the evaporation temperature Tu used to calculate meanvalue Tu ave is the temperature converted from detection pressure Ps ofpressure sensors 13 of operating outdoor units A.

ΔSHave is the change in mean value SHave of the degree of superheatingSH on the suction side of operating compressors 1. Specifically, thedegree of superheating SH used to calculate mean value SHave is a valueobtained by subtracting the evaporation temperature Tu converted fromdetection pressure Ts of pressure sensors 13 of operating outdoor unitsA from detection temperature Ts of temperature sensors 15 of theoperating outdoor units A (SH=Ts−Tu).

Qsum is the total degree of opening in the early phase of operation ofthe expansion valves provided immediately before the evaporators. Whencooling is applied, the degree of opening used to calculate Qsum is thedegree of opening of each indoor expansion valve 31. When heating isapplied, the degree of opening used to calculate Qsum is the degree ofopening of each outdoor expansion valve 4.

The above methods of calculating the parameters can be appropriatelymodified based on the positions of the temperature sensors or pressuresensors.

FIG. 2 is a p-h chart showing the behavior of the above refrigerationcycle in a cooling operation. FIG. 2 shows a cycle C1 in which there isno refrigerant leakage, a cycle C2 in which refrigerant leakage makessome progress, and a cycle C3 in which refrigerant leakage makes furtherprogress from cycle C2. The refrigerant at A1 is in a high-pressurestate where the refrigerant is compressed by the compressor 1. Thisrefrigerant in the high-pressure state is condensed by the outdoor heatexchanger 3 and reaches A2. Further, the refrigerant isadiabatically-expanded by expansion valves 4 and 31 and reaches A3.After the adiabatic expansion, the refrigerant is evaporated by theindoor heat exchanger 32 and reaches A4. In connection with theprogression of refrigerant leakage, the cycle moves in the direction ofhigh enthalpy and low pressure as a whole. FIG. 3 shows how the totaldegree of opening Qact changes in the procession of leakage. The totaldegree of opening Qact shown in FIG. 3 is the total degree of opening ofthe indoor expansion valves 31 when the degree of superheating of therefrigeration cycle is kept constant. The total degree of opening Qactincreases slowly at the beginning of leakage. When the leakage makessome progress, the total degree of opening Qact increases steeply.Subsequently, the total degree of opening Qact reaches the maximum totaldegree of opening Qmax. The maximum total degree of opening Qmax is thetotal degree of opening in a state where the indoor expansion valves 31are open to the maximum extent.

Now, this specification explains an example of a method of detectingleakage using the predictive total degree of opening Qpre and the actualtotal degree of opening Qact. In the graph of FIG. 4, the horizontalaxis represents the predictive total degree of opening Qpre, and thevertical axis represents the actual total degree of opening Qact. Thesolid line is the line of Qact Qpre. The dashed line is the line ofQact=Qpre+α. Setting value α is a threshold separating a case whererefrigerant leakage can be detected in the refrigeration cycle from acase where refrigerant leakage cannot be detected. For example, thesetting value may be determined experimentally, theoretically orempirically. For example, setting value α may be the degree of openingfor 200 to 300 pulses as the number of drive pulses. For example, in thepresent embodiment, the above detector detects refrigerant leakage whendifference ΔQ (=|Qpre−Qact|) between the predictive total degree ofopening Qpre and the actual total degree of opening Qact is greater thansetting value α (ΔQ>α).

Now, this specification explains the details of the operation of thecontroller 40 in connection with the detection of refrigerant leakage.Control related to the detection of refrigerant leakage differs betweenwhen cooling is applied and when heating is applied.

FIG. 5 is a flowchart showing an example of the operation of thecontroller 40 when cooling is applied. The controller 40 determineswhether a flag f is “0” (step 101). For example, the flag f is clearedto “0” when the user or operator presses the reset switch 42 ininstalling the refrigeration cycle device.

When the flag f is “0” (YES in step 101), the controller 40 calculatesthe operation time t (step 102) and determines whether the calculatedoperation time t is greater than or equal to a setting time t1 (step103). The calculated operation time t is updated and stored in thememory inside the controller 40 sequentially, and is cleared when thereset switch 42 is pressed. Setting time t1 is, for example, a timedetermined between 50 and 100 hours considered as the early phase ofoperation, and may be appropriately determined based on the environmentin which the refrigeration cycle device is installed. When thecalculated operation time t is less than setting time t1 (NO in step103), the process of the controller 40 returns to the determination ofstep 101.

When the calculated operation time t is greater than or equal to settingtime t1 (YES in step 103), the controller 40 determines whether therefrigeration cycle is stable (steps 104, 105 and 106). In step 104, thecontroller 40 determines whether the absolute value of difference ΔSHbetween the degree of superheating SH of the refrigerant on the suctionside of each operating compressor 1 and the target value SHt of thedegree of superheating SH is less than a setting value ΔSHs related tothe degree of superheating (|ΔSH|<ΔSHs). The target value SHt is set bythe controller 40 based on the operation conditions, etc. Setting value£SHs may be determined in advance in the range of, for example, 0 to 3K. In step 105, the controller 40 determines whether the degree ofsuperheating SH is positive (SH≧0). In step 106, the controller 40determines whether the operating frequency F of each operatingcompressor 1 is greater than or equal to a setting value Fs related tothe operating frequency (F≧Fs). Setting value Fs may be determined inadvance in the range of approximately 30% or more of the maximumoperating frequency in each compressor 1, preferably, in the range ofapproximately 40% or more. When any one of the results of determinationof steps 104 to 106 is negative, the operation of the controller 40returns to the determination of step 101.

When all of the results of determination of steps 104 to 106 areaffirmative, the controller 40 records the state quantity of therefrigeration cycle at this time point based on the determination thatthe refrigeration cycle enters a stable state (step 107). Specifically,the controller 40 detects Fsum, Tcj ave, Tg ave, Tu ave, SHave and Qsumat the present time point as the state quantity (second state quantity)of the early phase of operation (second time point), and stores thedetected state quantity in the internal memory. In the explanationbelow, Fsum, Tcj ave, Tg ave, Tu ave and SHave detected and stored instep 107 are referred to as Fsum′, Tcj ave′, Tg ave′, Tu ave′ andSHave′, respectively. The controller 40 sets the flag f to “1” afterrecording the state quantity of the early phase of operation (step 108).Subsequently, the operation of the controller 40 returns to thedetermination of step 101.

When the flag f is “1” (NO in step 101), the controller 40 determineswhether the refrigeration cycle is stable (steps 109, 110 and 111) in amanner similar to that of steps 104 to 106. Further, the controller 40determines whether the outside air temperature To is greater than orequal to a setting value Tos related to the outside air temperature(To≧Tos) (step 112). Setting value Tos may be set in advance in therange of, for example, 10 to 15° C. The outside air temperature To usedfor comparison with setting value Tos may be, for example, thetemperature detected by one of temperature sensors 17 of operatingoutdoor units A, or may be the mean value of the temperature detected bytemperature sensors 17 of operating outdoor units A. When any one of theresults of determination of steps 109 to 112 is negative, the operationof the controller 40 returns to the determination of step 101.

When all of the results of determination of steps 109 to 112 areaffirmative, the controller 40 detects, as the change in the state, thedifference between the state quantity of the early phase of operationstored in the internal memory and the state quantity of therefrigeration cycle at the present time point (step 113). Specifically,the controller 40 detects Fsum, Tcj ave, Tg ave, Tu ave, SHave and Qactat the present time point as the state quantity (first state quantity)at the present time point (first time point). Qact is the actual totaldegree of opening of the indoor expansion valves 31 at the present timepoint. The change in the state is ΔFsum (=Fsum−Fsum′), ΔTcj ave (=Tcjave−Tcj ave′), ΔTg ave (=Tg ave−Tg ave′), ΔTu ave (=Tu ave−Tu ave′), andΔSHave (=SHave−SHave′).

The controller 40 calculates the predictive total degree of opening Qpreof the indoor expansion valves 31 on the assumption that there is norefrigerant leakage in the refrigeration cycle, based on the detectedchange in the state, specifically, ΔFsum, ΔTcj ave, ΔTg ave, ΔTu ave andΔSHave, the total degree of opening Qsum of the early phase of operationstored in the internal memory, and equation (1) (step 114).

The controller 40 determines the presence or absence of refrigerantleakage based on the calculated predictive total degree of opening Qpreand the actual degree of opening Qact of the indoor expansion valves 31at the present time point (step 115). Specifically, the controller 40calculates difference ΔQ (=|Qpre−Q act|) between the predictive totaldegree of opening Qpre and the actual total degree of opening Qact, anddetermines whether difference ΔQ is greater than the above setting valueα (ΔQ>α).

When difference ΔQ is greater than setting value α (YES in step 115),the controller 40 indicates this fact by, for example, a characterdisplay or an icon image display with the remote controller 41 based onthe determination that there is refrigerant leakage in the refrigerationcycle (step 116). By this indication, the user is able to recognize thatrefrigerant leakage has occurred and request maintenance or inspection.

Further, the controller 40 suspends the compressors 1 and disables thesubsequent operation based on the indication (step 117). Thisdisablement prevents the operation from continuing during the leakage ofthe refrigerant. Thus, a detrimental effect on the refrigeration cycledevice can be avoided.

When difference ΔQ is less than or equal to setting value α (NO in step115), the amount of refrigerant of the refrigeration cycle is normal. Inthis case, the operation of the controller 40 returns to thedetermination of step 101 without going through steps 116 and 117.

Now, this specification explains an operation which is performed whenheating is applied.

FIG. 6 is a flowchart showing an example of the operation of thecontroller 40 when heating is applied. The controller 40 determineswhether the flag f is “0” (step 101). When the flag f is “0” (YES instep 101), the controller 40 performs steps 102 to 108 in a mannersimilar to that of a cooling operation. The state quantity (second statequantity) of the early phase of operation (second time point) detectedand stored in the internal memory in step 107 is Fsum′, Tcj ave′, Tgave′, Tu ave′, SHave′ and Qsum in a manner similar to that of a coolingoperation. Here, Tcj ave′ is the mean value of temperature T1 detectedby temperature sensors 16 of operating outdoor units A. Qsum is thetotal degree of opening of the outdoor expansion valves 4.

When the flag f is “1” (NO in step 101), the controller 40 determineswhether the operating rate R of each of indoor units B1 to Bm is greaterthan or equal to setting value Rs (step 201). The operating rate R isthe proportion of total horsepower Gact of indoor units B operating atthe present time point to total horsepower Gt of indoor units B1 to Bm(R=Gact/Gt). To explain the operating rate R, as an example, thisspecification assumes a refrigeration cycle device comprising indoorunit B1 having 4 HP (horsepower) and indoor units B2 to B5 having 2 HP.In this case, total horsepower Gt is 12 (=4+2+2+2+2) HP. For example,when all of indoor units B1 to B5 operate, the operating rate R is 100%(=12 HP/12 HP). When only outdoor unit B5 operates, the operating rate Ris 16.7% (=2 HP/12 HP).

When the operating rate R is less than setting value Rs (NO in step201), the operation of the controller 40 returns to the determination ofstep 101. In this case, detection of refrigerant leakage is notperformed.

When the operating rate R is greater than or equal to setting value Rs(YES in step 201), the controller 40 determines whether therefrigeration cycle is stable in a manner similar to that of a coolingoperation (steps 109, 110 and 111). In a heating operation, thedetermination regarding the outside air temperature To (step 112) is notperformed.

When all of the results of determination of steps 109 to 111 areaffirmative, the controller 40 performs the same steps as steps 113 to117 of a cooling operation. The state quantity (first state quantity) atthe present time point (first time point) detected in step 113 is Fsum,Tcj ave, Tg ave, Tu ave, SHave and Qact in a manner similar to that of acooling operation. Further, the change in the state is ΔFsum(=Fsum−Fsum′), ΔTcj ave (=Tcj ave−Tcj ave′), ΔTg ave (=Tg ave−Tg ave′),ΔTu ave (=Tu ave−Tu ave′) and ΔSHave (=SHave−SHave′) in a manner similarto that of a cooling operation. Here, Tcj ave is the mean value oftemperature T1 detected by temperature sensors 16 of operating outdoorunits A. Qact is the total degree of opening of the outdoor expansionvalves 4. The predictive total degree of opening Qpre calculated in step114 is the total degree of opening related to the outdoor expansionvalves 4. In step 115, the presence or absence of refrigerant leakage isdetermined by comparing difference ΔQ between the predictive totaldegree of opening Qpre calculated in step 114 and the actual totaldegree of opening Qact of the outdoor expansion valves 4 at the presenttime point with setting value α. Setting value α may be different fromthat of a cooling operation.

Step 201 is inserted into a heating operation to prevent erroneousdetection of refrigerant leakage because of a liquid refrigerant storedin suspended indoor units B. When heating is applied, each indoor heatexchanger 32 functions as a condenser, and the indoor expansion valves31 of suspended indoor units B are closed. Thus, a liquid refrigerant isstored in the indoor heat exchangers 32 of suspended indoor units B,etc. When a few indoor units B are under suspension (in other words,when the operating rate R is high), a sufficient amount of refrigerantis supplied to the refrigeration cycle from the liquid receivers 5 ofoutdoor units A1 to An. However, when a large number of indoor units Bare under suspension (in other words, when the operating rate R is low),the amount of refrigerant circulating in the refrigeration cycle isinsufficient. Thus, the liquid tube may have two phases, or the degreeof opening of each outdoor expansion valve 4 may be increased. Thus,even if no refrigerant leakage has occurred, refrigerant leakage may bedetected because of the increase in the total degree of opening Qactwhich is used to determine refrigerant leakage.

FIG. 7 is a conceptual diagram showing an example of the relationshipbetween the operating rate R and the possibility of implementation ofleakage determination. In this example, when the operating rate R is100%, 75%, 50% and 30%, the degree of opening Q of each outdoorexpansion valve 4 and the degree of superheating SH of the refrigeranton the suction side of each compressor 1 are stable after staring aheating operation. The deviations of the degree of opening Q and thedegree of superheating SH are small. In this case, the refrigerantcirculating in the refrigeration cycle does not cause erroneousdetection of refrigerant leakage in terms of the amount (thus, thedetermination of operating rate is “OK”). Therefore, the determinationof leakage is implemented. In contrast, when the operating rate R is15%, the degree of opening Q or the degree of superheating SH isunstable even after a certain amount of time. The deviations of thedegree of opening Q and the degree of superheating SH are large. In thiscase, the refrigerant circulating in the refrigeration cycle may causeerroneous detection of refrigerant leakage in terms of the amount (thus,the determination of operating rate is “NG”). Therefore, thedetermination of leakage is not implemented.

In the example of FIG. 7, for example, setting value Rs may be set toapproximately 30% as it is the lowest operating rate which does notproduce the behavior caused by a shortage of refrigerant. Setting valueRs may be fixed in advance, or may be appropriately changed afterinstalling the refrigeration cycle device.

FIG. 8 is a flowchart showing an example of the operation of thecontroller 40 when setting value Rs is appropriately changed. Forexample, the operation shown in this flowchart is performed when theflag f is “0” in a heating operation. The controller 40 determineswhether the calculated operation time t is greater than or equal to asetting value t2 (step 301). Setting time t2 is, for example, a timedetermined between 50 and 100 hours considered as the early phase ofoperation, and may be appropriately determined based on the environmentin which the refrigeration cycle device is installed. During a period inwhich the calculated operation time t is less than setting time t2 (NOin step 301), the controller 40 repeats the determination of step 301.

When the calculated operation time t is greater than or equal to settingtime t2 (YES in step 301), the controller 40 determines whether thedegree of opening Q of each outdoor expansion valve 4 is stable (step302). Specifically, the controller 40 determines whether the absolutevalue of the change ΔQx in the degree of opening Q of each outdoorexpansion valve 4 for each predetermined time is constantly less than asetting value Qs1 (|ΔQx|<Qs1) during a certain time t3. Thepredetermined time is the cycle for sampling the number of drive pulsesof each outdoor expansion valve 4 to calculate the change ΔQx, and is,for example, the cycle for performing step 302. Setting value Qs1 is avalue used to determine that the degree of opening Q of each outdoorexpansion valve 4 is stable. Setting value Qs1 is, for example, thedegree of opening for 5 to 10 pulses as the number of drive pulses. Forexample, certain time t3 may be determined in the range of 3 to 5minutes. When the result of determination of step 302 is negative (NO instep 302), the operation of the controller 40 returns to step 301.

When the result of determination of step 302 is affirmative (YES in step302), the controller 40 determines whether the current degree of openingQ of each outdoor expansion valve 4 is not the maximum degree of openingQmax of the outdoor expansion valves 4 (step 303). When the degree ofopening Q of at least one outdoor expansion valve 4 reaches the maximumdegree of opening Qmax (NO in step 303), there is a possibility that thedegree of opening Q of the outdoor expansion valve 4 is stable at themaximum degree of opening Qmax even though the amount of refrigerant ofthe refrigeration cycle is insufficient. In this case, the operation ofthe controller 40 returns to step 301.

When the degree of opening Q of all of the outdoor expansion valves 4 isless than the maximum degree of opening Qmax (YES in step 303), it maybe determined that the behavior caused by a shortage of refrigerantcirculating in the refrigeration cycle is not produced. The controller40 determines whether the current operating rate R is less than settingvalue Rs (R<Rs) (step 304). When the operating rate R is greater than orequal to setting value Rs (NO in step 304), the operation of thecontroller 40 returns to the determination of step 301. When theoperating rate R is less than setting value Rs (YES in step 304), thecontroller 40 updates setting value Rs with the current operating rate R(step 305).

For example, setting value Rs is set so as to be sufficiently large soonafter the refrigeration cycle device is installed. Subsequently, thesteps shown in the flowchart of FIG. 8 are repeated in a normaloperation. In connection with this repetition, setting value Rs isupdated with a smaller value in a range which does not produce thebehavior caused by a shortage of refrigerant.

As explained above, the refrigeration cycle device of the presentembodiment predicts the total degree of opening Qpre of the expansionvalves on the assumption that there is no refrigerant leakage, based onthe change from the state quantity of the early phase of operation ofthe refrigeration cycle to the current state quantity. The refrigerationcycle device further detects refrigerant leakage by comparing thepredictive total degree of opening Qpre with the actual total degree ofopening Qact at the present time point. In this manner, when the changefrom the state quantity of the early phase of operation to the currentstate quantity is used, it is possible to accurately predict the totaldegree of opening Qpre without relying on the number of indoor units Band the length of pipes in the refrigeration cycle. Thus, even if theleakage of refrigerant is less, the leakage can be surely detected.

Further, the present embodiment uses the total degree of opening of theexpansion valves provided immediately before the evaporators as aparameter for determining leakage when either cooling or heating isapplied. Normally, in a refrigeration cycle, the degree of opening of anexpansion valve provided immediately after a condenser is controlledsuch that the amount of supercooling of the condenser is constant. Thus,the density of the refrigerant on the inlet side of this expansion valvedoes not change without leakage of a substantial amount of refrigerant.However, the degree of opening of an expansion valve providedimmediately before an evaporator is controlled such that the degree ofsuperheating of the evaporator is constant. Thus, the sensitivity to thechange in the density of the refrigerant in the liquid pipe is high. Inthis manner, in the present embodiment, it is possible to detectrefrigerant leakage even if the leakage of refrigerant is less.

Moreover, in the present embodiment, on condition that the refrigerationcycle is stable, the initial state is stored, and refrigerant leakage isdetected. Thus, refrigerant leakage can be accurately detected.Especially, the following two conditions are used to determine whetherthe refrigeration cycle is stable. As the first condition, the absolutevalue of difference ΔSH between the degree of superheating SH and thetarget value SHt is less than setting value ΔSHs. As the secondcondition, the degree of superheating SH is positive. Thus, refrigerantleakage can be accurately detected in a state where there is noliquid-back, in which a liquid refrigerant is sucked by the compressors1, or there is no delay in the operation of the expansion valves. Whenthe operating frequency F is low, the liquid refrigerant may be storedin the outdoor heat exchangers 3 or the indoor heat exchangers 32. Inthis regard, a condition that the operating frequency F is greater thanor equal to setting value Fs is used to determine the stable state ofthe refrigeration cycle. Therefore, refrigerant leakage can beaccurately detected in a state where the liquid refrigerant is notstored in the outdoor heat exchangers 3 or the indoor heat exchangers32.

When the outside air temperature To is low in a cooling operation, theliquid refrigerant may be stored in the outdoor heat exchangers 3. Inthis regard, a condition that the outside air temperature To is greaterthan or equal to setting value Tos is used to perform leakage detection.Therefore, refrigerant leakage can be accurately detected in a statewhere the liquid refrigerant is not stored in the outdoor heatexchangers 3.

In the present embodiment, leakage detection is not performed when theoperating rate R is less than setting value Rs in a heating operation.Thus, it is possible to prevent erroneous detection of leakage caused bythe behavior of the refrigeration cycle with a low operating rate. Whenthere is an indoor unit B under suspension, the refrigerant is stored inthe indoor unit B. This structure decreases the redundant refrigerantstored in the liquid receivers 5, etc. Thus, when the operating rate Ris low in the range greater than or equal to setting value Rs, leakagecan be detected even with a smaller amount of leaked refrigerant.

[2] Second Embodiment

A second embodiment is explained. The structure of a refrigeration cycledevice is the same as that of the first embodiment. The same or similarelements are denoted by the same reference numbers. Thus, theexplanation of such elements may be omitted.

A controller 40 mainly functions as a detector, a recorder and anupdater in a manner similar to that of the first embodiment. However,the detector of the present embodiment calculates (predicts) apredictive total amount of supercooling (a first amount of supercooling)UCpre of each condenser at the present time point (a first time point)on the assumption that there is no refrigerant leakage in therefrigeration cycle, based on the change to the state quantity (a firststate quantity) of the refrigeration cycle at the present time pointfrom the state quantity (a second state quantity) of the refrigerationcycle in the early phase of operation (at a second time point). Thedetector detects refrigerant leakage of the refrigeration cycle bycomparing the actual total amount of supercooling (a second amount ofsupercooling) UCact of each condenser at the present time point with thepredictive total amount of supercooling UCpre.

The amount of supercooling UC of an outdoor heat exchanger 3 whichfunctions as a condenser in a cooling operation is, for example, thedifference (Tg−T1) between the saturated condensation temperature Tgconverted from the detection pressure Pd of a pressure sensor 12 of anoutdoor unit A and detection temperature T1 of an temperature sensor 16.In this case, the total amount of supercooling UCact is equivalent tothe total amount of supercooling UC of the outdoor heat exchangers 3 ofoperating indoor units A out of outdoor units A1 to An.

The amount of supercooling UC of an indoor heat exchanger 32 whichfunctions as a condenser in a heating operation is, for example, thedifference (Tg ave−T2) between the mean value Tg ave of the saturatedcondensation temperature Tg converted from the detection pressure Pd ofthe pressure sensors 12 of operating outdoor units A and detectiontemperature T2 of a temperature sensor 34 of an indoor unit B. In thiscase, the total amount of supercooling UCact is equivalent to the totalamount of supercooling UC of the indoor heat exchangers 32 of operatingindoor units B out of indoor units B1 to Bm.

A method of calculating the predictive total amount of supercoolingUCpre is explained.

In general, the amount of supercooling UC is determined based on theamount of refrigerant of the refrigeration cycle, the inner volume ofthe refrigeration cycle and the amount of heat transmission. The amountof heat transmission can be shown by the following theoretical formula.The left-hand side represents the amount of heat transmission on the airside. The right-hand side represents the amount of heat transmission onthe refrigerant side. K is the rate of heat passage (kW/m²K). A is thearea of heat transmission (m²). ΔT is the temperature difference (K)between the refrigerant and air. Gr is the flow rate (kg/h) ofrefrigerant. Δh is the difference in the specific enthalpy (kJ/kg).

Amount of heat transmission=K×A×ΔT=Gr×Δh

Assuming that the amount of refrigerant of the refrigeration cycle isconstant because there is no refrigerant leakage, and the inner volumeof the refrigeration cycle is constant, the current amount ofsupercooling UC can be predicted by correcting the amount ofsupercooling UC at a certain time point based on the change fromparameters related to the amount of heat transmission at the certaintime point to the same parameters at the present time point. Forexample, the parameters related to the amount of heat transmission maybe the operating frequency of a compressor 1, the condensationtemperature, the evaporation temperature, the degree of superheating andthe outside air temperature.

Specifically, the predictive total amount of supercooling UCpre is givenby

UCpre=a2·ΔFsum+b2·ΔTg ave+c2·ΔTu ave+d2·ΔSHave+e2·ΔTo ave+UCsum,  (2)

where a2, b2, c2, d2 and e2 are constants and may be determinedexperimentally, theoretically or empirically, and ΔFsum, ΔTg ave, ΔTuave and ΔSHave are the same parameters as in equation (1).

ΔTo ave is the change in mean value To ave of detection temperature Toof temperature sensors 17 of operating outdoor units A. UCsum is thetotal amount of supercooling of the condensers in the early phase ofoperation. In a cooling operation, the amount of supercooling UC used tocalculate UCsum is the difference between the saturated condensationtemperature Tg converted from the detection pressure Pd of the pressuresensor 12 of each operating outdoor unit A and detection temperature T1of temperature sensor 16 of each operating outdoor unit A. In a heatingoperation, the amount of supercooling UC used to calculate UCsum is, forexample, the difference between the above mean value Tg ave anddetection temperature T2 of temperature sensor 34 of each indoor unit B.

Now, this specification explains an example of a method of detectingleakage using the predictive total amount of supercooling UCpre and theactual total amount of supercooling UCact. In the graph of FIG. 9, thehorizontal axis represents the predictive total amount of supercoolingUCpre, and the vertical axis represents the actual total amount ofsupercooling UCact. The solid line is the line of UCact=UCpre. Thedashed lines are the lines of UCact=UCpre+β, and UCact=UCpre−β. Settingvalue β is a threshold separating a case where refrigerant leakage canbe detected in the refrigeration cycle from a case where refrigerantleakage cannot be detected. For example, the setting value may bedetermined experimentally, theoretically or empirically. For example,setting value β may be determined in the range of 3 to 5 K. In thepresent embodiment, the above means for detection detects refrigerantleakage when the difference ΔUC (=|UCpre−UCact|) between the predictivetotal amount of supercooling UCpre and the actual total amount ofsupercooling UCact is greater than setting value β (ΔUC>β). In thecoordinate system of FIG. 9, refrigerant leakage is detected when thedot determined by the total amounts of supercooling UCpre and UCact isnot present between the two dashed lines.

As an example, FIG. 10 shows the results of the calculation of thepredictive total amount of supercooling UCpre and the measurement of theactual total amount of supercooling UCact in a case where a regularamount of refrigerant is filled in the refrigeration cycle, and in acase where the amount of the refrigerant filled in the refrigerationcycle is equivalent to leakage of 20%. The horizontal axis representsthe predictive total amount of supercooling UCpre. The vertical axisrepresents the actual total amount of supercooling UCact. The dashedlines are the lines of UCact=UCpre+β and UCact=UCpre−β. The solid lineis the approximate line of a plot related to the regular amount ofrefrigerant and substantially conforms to the line of UCact=UCpre. Thealternate long and short dash line is the approximate line of a plotrelated to the amount of refrigerant equivalent to leakage of 20%.

In the example of FIG. 10, setting value β is 3 K. The plot related tothe regular amount of refrigerant and its approximate line aresubstantially in the range of ΔUC≦β. The plot related to the amount ofrefrigerant equivalent to leakage of 20% and its approximate line aremostly in the range of ΔUC>β. The above results reveal that refrigerantleakage can be detected by comparing the predictive total amount ofsupercooling UCpre with the actual total amount of supercooling UCact.

Now, this specification explains the details of the operation of thecontroller 40 in connection with the detection of refrigerant leakage.

In a cooling operation, the controller 40 operates in line with theflowchart of FIG. 5 in a manner similar to that of the first embodiment.However, the state quantity (second state quantity) of the early phaseof operation (second time point) detected and stored in the internalmemory in step 107 is Fsum, Tg ave, Tu ave, SHave, To ave and UCsum atthis time point. UCsum is the total amount of supercooling UC related tothe outdoor heat exchangers 3 of operating outdoor units A at the timeof step 107. In the explanation below, Fsum, Tg ave, Tu ave, SHave andTo ave detected and stored in step 107 are referred to as Fsum′, Tgave′, Tu ave′, SHave′ and To ave′, respectively.

The state quantity (first state quantity) detected in step 113 is Fsum,Tg ave, Tu ave, SHave, To ave and UCact at the time point (first timepoint). UCact is the total amount of supercooling UC related to theoutdoor heat exchangers 3 of operating outdoor units A at the time ofstep 113. The change in the state detected in step 113 is ΔFsum(=Fsum−Fsum′), ΔTg ave (=Tg ave−Tg ave′), ΔTu ave (=Tu ave−Tu ave′),ΔSHave (=SHave−SHave′), and ΔTo ave (=To ave−To ave′).

In step 114, the predictive total amount of supercooling UCpre iscalculated based on the detected change in the state, specifically,ΔFsum, ΔTg ave, ΔTu aye, ΔSHave and ΔTo ave, the total amount ofsupercooling UCsum in the early phase of operation stored in theinternal memory, and equation (2). In step 115, the presence or absenceof refrigerant leakage is determined by comparing the difference ΔUCbetween the predictive total amount of supercooling UCpre calculated instep 114 and the current total amount of supercooling UCact of theoutdoor heat exchangers 3 with setting value β.

In a heating operation, the controller 40 operates in line with theflowchart of FIG. 6 in a manner similar to that of the first embodiment.The state quantity (second state quantity) of the early phase ofoperation (second time point) detected and stored in the internal memoryin step 107 is Fsum′, Tg ave′, Tu ave′, SHave′, To ave′ and UCsum in amanner similar to that of a cooling operation. However, UCsum is thetotal amount of supercooling UC related to the indoor heat exchangers32.

The state quantity (first state quantity) at the present time point(first time point) detected in step 113 is Fsum, Tg ave, Tu ave, SHave,To ave and UCact in a manner similar to that of a cooling operation. Thechange in the state is ΔFsum (=Fsum−Fsum′), ΔTg ave (=Tg ave−Tg ave′),ΔTu ave (=Tu ave−Tu ave′), ΔSHave (=SHave−SHave′) and ΔTo ave (=Toave−To ave′). However, UCact is the total amount of supercooling UCrelated to the indoor heat exchangers 32 of operating indoor units B atthe time of step 113. The predictive total amount of supercooling UCprecalculated in step 114 is the predictive total amount of supercoolingrelated to the indoor heat exchangers 32. In step 115, the presence orabsence of refrigerant leakage is determined by comparing the differenceLUC between the predictive total amount of supercooling UCpre calculatedin step 114 and the current total amount of supercooling UCact of theindoor heat exchangers 32 with setting value β. Setting value β may bedifferent from that of a cooling operation.

The flow of the operation for updating a setting value Rs is the same asthat of the flowchart of FIG. 8.

As explained above, in the present embodiment, refrigerant leakage canbe accurately detected in a manner similar to that of the firstembodiment even if refrigerant leakage is detected by comparing thepredictive total amount of supercooling UCpre with the actual totalamount of supercooling UCact.

[3] Modification Examples

Some modification examples are explained.

Regarding the determination of the stable state of the refrigerationcycle, steps 401 and 402 shown in FIG. 11 and FIG. 12 may be used inplace of steps 104 and 109. In steps 401 and 402 of the flowchart(cooling operation) of FIG. 11, the controller 40 determines whether theabsolute value of the change ΔQx in the degree of opening Q of eachindoor expansion valve 31 for each predetermined time is constantly lessthan a setting value Qs2 (|ΔQx|<Qs2) during a certain time t4. In steps401 and 402 of the flowchart (heating operation) of FIG. 12, thecontroller 40 determines whether the absolute value of the change ΔQx inthe degree of opening Q of each outdoor expansion valve 4 for eachpredetermined time is constantly less than setting value Qs2 (|ΔQx|<Qs2)during certain time t4. The predetermined time is the cycle for samplingthe number of drive pulses of each indoor expansion valve 31 or eachoutdoor expansion valve 4 to calculate the change ΔQx, and may be, forexample, the cycle for performing steps 401 and 402. Setting value Qs2is a value used to determine that the degree of opening Q of eachoutdoor expansion valve 4 or each indoor expansion valve 31 is stable.Setting value Qs2 may be, for example, the degree of opening for 3 to 5pulses as the number of drive pulses. For example, certain time t4 maybe determined in the range of 5 to 10 minutes.

In general, in a multi-type air conditioner, the design of an indoorunit or the length of pipes is very flexible. Therefore, the structureof the system may be changed after installing the air conditioner. Whena parameter which heavily relies on an indoor unit or the length ofpipes is included in the formulae for calculating the predictive totaldegree of opening Qpre and the predictive total amount of supercoolingUCpre, the formulae need to be defined again in connection with thechange in the structure of the system. To solve this problem, thepredictive total degree of opening Qpre and the predictive total amountof supercooling UCpre may be calculated by formulae defined so as not toinclude a parameter which heavily relies on an indoor unit or the lengthof pipes. For example, the evaporation temperature Tu and the degree ofsuperheating SH on the suction side of each compressor 1 heavily rely onthe indoor unit or the length of pipes. Thus, formulae may be defined soas not to include them.

In step 305 of the flowchart of FIG. 8, setting value Rs may be updatedwith an operating rate which is higher than the current operating rate Rby only a predetermined value. The amount of liquid refrigerant storedin suspended indoor units and pipes around the indoor units changesbased on the indoor arrangement such as the length of pipes connectingthe indoor units to the respective outdoor units. Thus, when theoperating rate R is the same, but the suspended indoor units differ, thebehavior caused by a shortage of refrigerant may be produced in one ofthem, and may not be produced in the other. It is possible to preventerroneous detection of refrigerant leakage caused by the difference inindoor arrangement by updating setting value Rs in the above manner.

The process for updating setting value Rs in the flowchart of FIG. 8 maybe performed while the operating rate is changed forcibly in a testoperation when the refrigeration cycle device is installed, instead ofin a normal operation.

Refrigeration cycle devices mounted on air conditioners are explained inthe above embodiments and modification examples. However, the structuresrelated to the detection of refrigerant leakage disclosed in the aboveembodiments and modification examples may be also applied torefrigeration cycle devices mounted on other devices such as hot-watersupply devices.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel embodiments described hereinmay be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the embodimentsdescribed herein may be made without departing from the spirit of theinventions. The accompanying claims and their equivalents are intendedto cover such forms or modifications as would fall within the scope andspirit of the inventions.

What is claimed is:
 1. A refrigeration cycle device comprising: arefrigeration cycle which returns a refrigerant discharged from acompressor to the compressor via a condenser, a plurality of expansionvalves and a plurality of evaporators connected to the expansion valves,respectively; and a detector which predicts a first total degree ofopening of the expansion valves at a first time point on the assumptionthat there is no refrigerant leakage in the refrigeration cycle, basedon a change to a first state quantity of the refrigeration cycle at thefirst time point from a second state quantity of the refrigeration cycleat a second time point earlier than the first time point, the detectordetecting refrigerant leakage of the refrigeration cycle by comparingthe first total degree of opening with a second total degree of openingwhich is an actual total degree of opening of the expansion valves atthe first time point.
 2. The refrigeration cycle device of claim 1,further comprising a plurality of indoor units each comprising an indoorheat exchanger functioning as the condenser in a heating operation,wherein in the heating operation, the detector performs the detection ofrefrigerant leakage in a state where an operating rate of the indoorunits is higher than a setting value related to the operating rate. 3.The refrigeration cycle device of claim 2, further comprising an updaterwhich updates the setting value in accordance with the operating rate ofthe indoor units in a state where the degree of opening of each of theexpansion valves is less than a maximum degree of opening and constantlystable for a certain time in the heating operation.
 4. The refrigerationcycle device of claim 1, wherein the detector performs the detection ofrefrigerant leakage in a state where a frequency of the compressor isgreater than or equal to a setting value related to the frequency. 5.The refrigeration cycle device of claim 1, wherein in a coolingoperation, the detector performs the detection of refrigerant leakage ina state where an outside air temperature is greater than or equal to asetting value related to the outside air temperature.
 6. A refrigerationcycle device comprising: a refrigeration cycle which returns arefrigerant discharged from a compressor to the compressor via acondenser, an expansion valve and an evaporator; and a detector whichpredicts a first amount of supercooling of the condenser at a first timepoint on the assumption that there is no refrigerant leakage in therefrigeration cycle, based on a change to a first state quantity of therefrigeration cycle at the first time point from a second state quantityof the refrigeration cycle at a second time point earlier than the firsttime point, the detector detecting refrigerant leakage of therefrigeration cycle by comparing the first amount of supercooling with asecond amount of supercooling which is an actual amount of supercoolingof the condenser at the first time point.
 7. The refrigeration cycledevice of claim 6, further comprising a plurality of indoor units eachcomprising an indoor heat exchanger functioning as the condenser in aheating operation, wherein in the heating operation, the detectorperforms the detection of refrigerant leakage in a state where anoperating rate of the indoor units is higher than a setting valuerelated to the operating rate.
 8. The refrigeration cycle device ofclaim 7, further comprising an updater which updates the setting valuein accordance with the operating rate of the indoor units in a statewhere a degree of opening of the expansion valve is less than a maximumdegree of opening and constantly stable for a certain time in theheating operation.
 9. The refrigeration cycle device of claim 6, whereinthe detector performs the detection of refrigerant leakage in a statewhere a frequency of the compressor is greater than or equal to asetting value related to the frequency.
 10. The refrigeration cycledevice of claim 6, wherein in a cooling operation, the detector performsthe detection of refrigerant leakage in a state where an outside airtemperature is greater than or equal to a setting value related to theoutside air temperature.